The present invention relates to an opening/closing device suitable in use for supporting an opening/closing member such as a shield in opening and closing with regard to an opened/closed member such as a helmet body, so that the above-mentioned opening/closing member can stop at any opening/closing position as well as a helmet equipped with such an opening/closing device.
For example as a helmet, the one equipped with a helmet body having an opening portion on a front surface and a shield for opening and closing the opening portion is commonly known, wherein the shield is opened and closed with regard to the helmet body using opening/closing devices in such a manner that the shield can stop at any position. In this helmet, end portions of the shield are rotatably jointed via the opening/closing devices to side portions of the helmet body, and thus the opening can be covered or exposed as appropriate.
As opening/closing devices of this type, the ones have been already proposed in JP Utility Model Registration No. 2541873, wherein the opening/closing devices support a shield so as to be openable/closable with regard to a helmet body, and generate a friction torque between the helmet body and the shield in an opening/closing direction so that the shield can be opened/closed with regard to the helmet body so as to stop at any opening/closing position.
Opening/closing devices as disclosed in the commonly known document are equipped with guide members provided on both side portions of a helmet body for openably/closably supporting both end portions of a shield and friction torque generation means which generate a friction torque between the helmet body and the shield, which forces the shield to stop at any opening/closing position. The friction torque generation means here generates a friction torque around a respective axis of shaft bodies which pivotally support the shield so as to be openable/closable with regard to the helmet body, and in this manner enable a stop of the shield at any opened/closed position with regard to the helmet body.
Nevertheless, in friction torque generation means which, as are the case with opening/closing devices disclosed in the above-mentioned commonly known document, generate a friction torque around a respective axis of shaft bodies, a sufficient rotational resistance cannot always be generated, which can cause the shield once opened to slip off. If one wishes to obtain a friction torque necessary to avoid this, a large friction area will be necessary, which leads to a problem of an increase in size of opening/closing devices.
On the other hand, if opening/closing devices are so designed that positions for friction generation are located at points radially distant from respective centers of rotation of a shield, the devices are of simple structure, and enable, even in a small size, to ensure a great rotational resistance. However, if for example groove portions in a shape of circle which is large (in radius) are formed on the shield itself for the above-mentioned purpose, problems arise in that the grooves in a shape of circle are hindrance to vision or factors unfavorable in terms of strength (factors such as those facilitating the generation of cracks).
On the other hand, opening/closing devices, even in a small size, requiring a large friction torque are also needed, except for a helmet, in opening/closing a first casing as opened/closed member provided with an operation portion, and a second casing as opening/closing member provided with a display device, the both casings being of a small-sized portable equipment such as a portable phone, a PDA and a notebook PC.